Piperazine bis-amide derivatives and their use as antagonists of the orexin receptor

ABSTRACT

This invention relates to piperazine bis-amide derivatives and their use as pharmaceuticals.

This invention relates to piperazine bis-amide derivatives and their useas pharmaceuticals.

Many medically significant biological processes are mediated by proteinsparticipating in signal transduction pathways that involve G-proteinsand/or second messengers.

Polypeptides and polynucleotides encoding the human 7-transmembraneG-protein coupled neuropeptide receptor, orexin-1 (HFGAN72), have beenidentified and are disclosed in EP-A-875565, EP-A-875566 and WO96/34877. Polypeptides and polynucleotides encoding a second humanorexin receptor, orexin-2 (HFGANP), have been identified and aredisclosed in EP-A-893498.

Polypeptides and polynucleotides encoding polypeptides which are ligandsfor the orexin-1 receptor, e.g. orexin-A (Lig72A) are disclosed inEP-A-849361.

Orexin receptors are found in the mammalian host and may be responsiblefor many biological functions, including pathologies including, but notlimited to, depression; anxiety; addictions; obsessive compulsivedisorder; affective neurosis/disorder; depressive neurosis/disorder;anxiety neurosis; dysthymic disorder; behaviour disorder; mood disorder;sexual dysfunction; psychosexual dysfunction; sex disorder; sexualdisorder; schizophrenia; manic depression; delerium; dementia; severemental retardation and dyskinesias such as Huntington's disease andGilles de la Tourett's syndrome; disturbed biological and circadianrhythms; feeding disorders, such as anorexia, bulimia, cachexia, andobesity; diabetes; appetite/taste disorders; vomiting/nausea; asthma;cancer; Parkinson's disease; Cushing's syndrome/disease; basophiladenoma; prolactinoma; hyperprolactinemia; hypopituitarism; hypophysistumor/adenoma; hypothalamic diseases; Froehlich's syndrome;adrenohypophysis disease; hypophysis disease; hypophysis tumor/adenoma;pituitary growth hormone; adrenohypophysis hypofunction;adrenohypophysis hyperfunction; hypothalamic hypogonadism; Kallman'ssyndrome (anosmia, hyposmia); functional or psychogenic amenorrhea;hypopituitarism; hypothalamic hypothyroidism; hypothalamic-adrenaldysfunction; idiopathic hyperprolactinemia; hypothalamic disorders ofgrowth hormone deficiency; idiopathic growth hormone deficiency;dwarfism; gigantism; acromegaly; disturbed biological and circadianrhythms; and sleep disturbances associated with such diseases asneurological disorders, neuropathic pain and restless leg syndrome,heart and lung diseases; acute and congestive heart failure;hypotension; hypertension; urinary retention; osteoporosis; anginapectoris; myocardial infarction; ischaemic or haemorrhagic stroke;subarachnoid haemorrhage; head injury such as sub-arachnoid haemorrhageassociated with traumatic head injury; ulcers; allergies; benignprostatic hypertrophy; chronic renal failure; renal disease; impairedglucose tolerance; migraine; hyperalgesia; pain; enhanced or exaggeratedsensitivity to pain, such as hyperalgesia, causalgia and allodynia;acute pain; burn pain; atypical facial pain; neuropathic pain; backpain; complex regional pain syndromes I and II; arthritic pain; sportsinjury pain; pain related to infection, e.g. FHV, post-polio syndrome,and post-herpetic neuralgia; phantom limb pain; labour pain; cancerpain; post-chemotherapy pain; post-stroke pain; post-operative pain;neuralgia; conditions associated with visceral pain including irritablebowel syndrome, migraine and angina; urinary bladder incontinence e.g.urge incontinence; tolerance to narcotics or withdrawal from narcotics;sleep disorders; sleep apnea; narcolepsy; insomnia; parasomnia; jet-lagsyndrome; and neurodegenerative disorders, which includes nosologicalentities such as disinhibition-dementia-parkinsonism-amyotrophy complex;pallido-ponto-nigral degeneration, epilepsy, and seizure disorders.

Experiments have shown that central administration of the ligandorexin-A (described in more detail below) stimulated food intake infreely-feeding rats during a 4 hour time period. This increase wasapproximately four-fold over control rats receiving vehicle. These datasuggest that orexin-A may be an endogenous regulator of appetite.Therefore, antagonists of its receptor may be useful in the treatment ofobesity and diabetes, see Cell, 1998, 92, 573-585.

There is a significant incidence of obesity in westernised societies.According to WHO definitions a mean of 35% of subjects in 39 studieswere overweight and a further 22% clinically obese. It has beenestimated that 5.7% of all healthcare costs in the USA are a consequenceof obesity. About 85% of Type 2 diabetics are obese, and diet andexercise are of value in all diabetics. The incidence of diagnoseddiabetes in westernised countries is typically 5% and there areestimated to be an equal number undiagnosed. The incidence of bothdiseases is rising, demonstrating the inadequacy of current treatmentswhich may be either ineffective or have toxicity risks includingcardiovascular effects. Treatment of diabetes with sulfonylureas orinsulin can cause hypoglycaemia, whilst metformin causes GIside-effects. No drug treatment for Type 2 diabetes has been shown toreduce the long-term complications of the disease. Insulin sensitiserswill be useful for many diabetics, however they do not have ananti-obesity effect.

Rat sleep/EEG studies have also shown that central administration oforexin-A, an agonist of the orexin receptors, causes a dose-relatedincrease in arousal, largely at the expense of a reduction inparadoxical sleep and slow wave sleep 2, when administered at the onsetof the normal sleep period. Therefore antagonists of its receptor may beuseful in the treatment of sleep disorders including insomnia.

The present invention provides piperazine bis-amide derivatives whichare non-peptide antagonists of human orexin receptors, in particularorexin-1 receptors. In particular, these compounds are of potential usein the treatment of obesity, including obesity observed in Type 2(non-insulin-dependent) diabetes patients, and/or sleep disorders. Thesecompounds may also be useful in the treatment of stroke, particularlyischaemic or haemorrhagic stroke. Additionally these compounds areuseful in stroke, particularly ischemic or haemorrhagic stroke, and/orblocking the emetic response i.e. the compounds are useful in thetreatment of nausea and vomiting.

International Patent Applications WO 99/09024, WO 99/58533, WO 00/47577and WO 00/47580 disclose phenyl urea derivatives and WO 00/47576discloses quinolinyl cinnamide derivatives as orexin receptorantagonists. WO01/96302 discloses N-aroyl cyclic amine derivatives andWO 02/44172 discloses morpholine derivatives as orexin receptorantagonists.

According to the invention there is provided compounds of formula (1):

wherein:

Y represents hydrogen or (C₁₋₆) alkyl;

Ar represents an aryl group or a 5- or 6-membered heterocyclic ringcontaining up to 3 heteroatoms selected from N, O and S, wherein thearyl or heterocyclic group is substituted by R¹ and further optionalsubstituents;

R¹ represents optionally substituted (C₁₋₆)alkoxy, halo, optionallysubstituted (C₁₋₆)alkyl, cyano, optionally substituted phenyl or anoptionally substituted 5- or 6-membered heterocyclic ring containing upto 4 heteroatoms selected from N, O and S;

R represents an optionally substituted aryl or an optionally substitutedheterocyclic ring system containing up to 4 heteroatoms selected from N,O and S;

or pharmaceutically acceptable derivatives thereof.

The term “aryl” includes single and fused rings, of which at least oneis aromatic, which rings may be unsubstituted or substituted by, forexample, up to three substituents as set out above. Each ring suitablyhas 5 or 6 ring atoms. When used herein in the definition of the Argroup, the term “aryl” includes phenyl or naphthyl. Suitably any arylgroup, including phenyl, may be optionally substituted by up to five,preferably up to three substituents.

When used herein the term “heterocyclic” suitably includes, unlessotherwise defined, aromatic and non-aromatic, single and fused, ringssuitably containing up to four heteroatoms in each ring, each of whichis selected from O, N and S, which rings, may be unsubstituted orsubstituted by, for example, up to three substituents. Each ringsuitably has 5 or 6 ring atoms. A fused heterocyclic ring system mayinclude carbocyclic rings and need include only one heterocyclic ring.

Preferably when R¹ represents an optionally substituted 5- or 6-memberedheterocyclic ring it contains up to 3 heteroatoms selected from N, O andS.

Preferably when R represents an optionally substituted heterocyclic ringsystem it contains up to 3 heteroatoms selected from N, O and S.

Examples of 5- or 6-membered “heterocyclic” rings include furanyl,pyrrolyl, thienyl, oxazolyl, thiazolyl, imidazolyl, oxadiazolyl,thiadiazolyl, pyridinyl, triazolyl, triazinyl, pyridazyl, pyrimidinyl,isothiazolyl, isoxazolyl, pyrazinyl or pyrazolyl.

Examples of fused heterocyclic rings include quinoxalinyl, quinazolinyl,pyridopyrazinyl, benzoxazolyl, benzothiophenyl, benzimidazolyl,naphthridinyl, quinolinyl, benzofuranyl, indolinyl or isoquinolinyl.

Y is preferably hydrogen or methyl.

Preferably where Ar represents an optionally substituted phenyl ring orand optionally substituted 5- or 6-membered heterocyclic groupcontaining up to 3 heteroatoms selected from N, O and S, the R¹ group issituated adjacent to the point of attachment to the amide carbonyl.

Ar preferably represents an optionally substituted phenyl, pyrazolyl orthiazolyl, more preferably thiazolyl.

Preferably R¹ represents an optionally substituted phenyl or furanyl,more preferably an optionally substituted phenyl.

Preferably R is optionally substituted 5- or 6-membered heterocyclicgroup containing up to 3 heteroatoms selected from N, O and S or anoptionally substituted fused heterocyclic ring system

Preferably R is an optionally substituted fused heterocyclic ringsystem.

More preferably R represents an optionally substituted benzofuranyl,quinolinyl or indolinyl, even more preferably R represents an optionallysubstituted benzofuranyl or quinolinyl.

Optional substituents for the groups Ar, R and R¹ include halogen,hydroxy, oxo, cyano, nitro, (C₁₋₆)alkyl, (C₁₋₆)alkoxy, aryl,halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy, aryl(C₁₋₆)alkoxy, (C₁₋₆)alkylthio,hydroxy(C₁₋₆)alkyl, (C₁₋₆)alkoxy(C₁₋₆)alkyl,(C₃₋₆)cycloalkyl(C₁₋₆)alkoxy, (C₁₋₆)alkanoyl, (C₁₋₆)alkoxycarbonyl,(C₁₋₆)alkylsulfonyl, (C₁₋₆)alkylsulfonyloxy,(C₁₋₆)alkylsulfonyl(C₁₋₆)alkyl, arylsulfonyl, arylsulfonyloxy,arylsulfonyl(C₁₋₆)alkyl, (C₁₋₆)alkylsulfonamido, (C₁₋₆)alkylamido,(C₁₋₆)alkylsulfonamido(C₁₋₆)alkyl, (C₁₋₆)alkylamido(C₁₋₆)alkyl,arylsulfonamido, arylcarboxamido, arylsulfonamido(C₁₋₆)alkyl,arylcarboxamido(C₁₋₆)alkyl, aroyl, aroyl(C₁₋₆)alkyl, oraryl(C₁₋₆)alkanoyl group; a group R³R⁴N—, R³OCO(CH₂)_(r),R³CON(R⁴)(CH₂)_(r), R³R⁴NCO(CH₂)_(r), R³R⁴NSO₂(CH₂)_(r) orR³SO₂NR⁴(CH₂)_(r) where each of R³ and R⁴ independently represents ahydrogen atom or a (C₁₋₆)alkyl group or where appropriate R³R⁴ formspart of a (C₃₋₆)azacyloalkane or (C₃₋₆)(2-oxo)azacycloalkane ring and rrepresents zero or an integer from 1 to 4. Additionally when thesubstituent is R³R⁴N(CH₂)_(n)— or R³R⁴N(CH₂)nO, R³ with at least one CH₂of the (CH₂)_(n) portion of the group form a (C₃₋₆)azacycloalkane and R⁴represents hydrogen, a (C₁₋₄)alkyl group or with the nitrogen to whichit is attached forms a second (C₃₋₆)azacycloalkane fused to the first(C₃₋₆)azacycloalkane.

Preferably, substituents for Ar are selected from halogen or optionallysubstituted phenyl, optionally substituted (C₁₋₆)alkyl or optionallysubstituted (C₁₋₆)alkoxy.

Preferably, substituents for R¹ are selected from halogen or optionallysubstituted (C₁₋₆)alkyl or optionally substituted (C₁₋₆)alkoxy.

Preferably, substituents for R are selected from halogen or optionallysubstituted phenyl, optionally substituted (C₁₋₆)alkyl or optionallysubstituted (C₁₋₆)alkoxy.

More preferably R is optionally substituted by a halogen, or optionallysubstituted (C₁₋₆)alkoxy.

The preferred substituent for Ar is methyl.

The preferred substituent for R¹ is fluorine.

The preferred substituents for R are selected from methoxy and fluorine.

Preferred compounds of the invention are selected from: Example Name 1(RS)-2-((Benzofuran-4-yl)carbonylaminomethyl)-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4- methylpiperazine 2Quinoline-8-carboxylic acid (1-{1-[5-(4-fluoro-phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-4-methyl-piperazin-2-ylmethyl)-amide 3 5-Methoxy-benzofuran-4-carboxylic acid(1-{1-[5-(4- fluoro-phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-4-methyl-piperazin-2-ylmethyl)-amide 4 Benzofuran-4-carboxylic acid(1-{1-[5-(4-fluoro- phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-piperazin-2-ylmethyl)-amide 5 Benzofuran-7-carboxylic acid (1-{1-[5-(4-fluoro-phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-piperazin- 2-ylmethyl)-amide 65-Fluoro-benzofuran-7-carboxylic acid (1-{1-[5-(4-fluoro-phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-piperazin-2-ylmethyl)-amide 7 Quinoline-8-carboxylic acid(1-{1-[5-(4-fluoro- phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-piperazin-2-ylmethyl)-amide 8 6-Methoxy-benzofuran-4-carboxylic acid (1-{1-[5-(4-fluoro-phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-piperazin-2-ylmethyl)-amide 9 7-Methoxy-benzofuran-4-carboxylic acid(1-{1-[5-(4- fluoro-phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-piperazin-2-ylmethyl)-amide 10 5-Methoxy-benzofuran-4-carboxylic acid(1-{1-[5-(4- fluoro-phenyl)-2-methyl-thiazol-4-yl]-methanoyl}-piperazin-2-ylmethyl)-amide 11 (S)-2-(((1-(6-Fluoro-2,3-dihydro-indol-1-yl)carbonyl)amino)methyl)-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-piperazine trifluoroacetate 12(S)-2-(((1-(6-Fluoro-2,3-dihydro-indol-1-yl)carbonyl)amino)methyl)-1-((2-(2- furanyl)phenyl)carbonyl)-piperazinetrifluoroacetateand pharmaceutically acceptable derivatives thereof.In the groups R and Ar, substituents positioned ortho to one another maybe linked to form a ring.

When a halogen atom is present in the compound of formula (I) it may befluorine, chlorine, bromine or iodine.

When the compound of formula (I) contains an alkyl group, whether aloneor forming part of a larger group, e.g. alkoxy or alkylthio, the alkylgroup may be straight chain, branched or cyclic, or combinationsthereof, it is preferably methyl or ethyl.

It will be appreciated that compounds of formula (I) may exist as R or Senantiomers. The present invention includes within its scope all suchisomers, including mixtures. Where additional chiral centres are presentin compounds of formula (I), the present invention includes within itsscope all possible diastereoismers, including mixtures thereof. Thedifferent isomeric forms may be separated or resolved one from the otherby conventional methods, or any given isomer may be obtained byconventional synthetic methods or by stereospecific or asymmetricsyntheses.

The subject invention also includes isotopically-labeled compounds,which are identical to those recited in formula (I) and following, butfor the fact that one or more atoms are replaced by an atom having anatomic mass or mass number different from the atomic mass or mass numberusually found in nature. Examples of isotopes that can be incorporatedinto compounds of the invention include isotopes of hydrogen, carbon,nitrogen, oxygen, phosphorous, fluorine, iodine, and chlorine, such as³H, ¹¹C, ¹⁴C, ¹⁸F, ¹²³I and ¹²⁵I.

Compounds of the present invention and pharmaceutically acceptablederivatives of said compounds that contain the aforementioned isotopesand/or other isotopes of other atoms are within the scope of the presentinvention. Isotopically-labeled compounds of the present invention, forexample those into which radioactive isotopes such as ³H, ¹⁴C areincorporated, are useful in drug and/or substrate tissue distributionassays. Tritiated, i.e., ³H, and carbon-14, i.e., ¹⁴C, isotopes areparticularly preferred for their ease of preparation and detectability.¹¹C and ⁸F isotopes are particularly useful in PET (positron emissiontomography), and ¹²⁵I isotopes are particularly useful in SPECT (singlephoton emission computerized tomography), all useful in brain imaging.Further, substitution with heavier isotopes such as deuterium, i.e., ²H,can afford certain therapeutic advantages resulting from greatermetabolic stability, for example increased in vivo half-life or reduceddosage requirements and, hence, may be preferred in some circumstances.Isotopically labeled compounds of formula (I) and following of thisinvention can generally be prepared by carrying out the proceduresdisclosed in the Schemes and/or in the Examples below, by substituting areadily available isotopically labeled reagent for a non-isotopicallylabeled reagent.

It will be understood that the invention includes pharmaceuticallyacceptable derivatives of compounds of formula (I) and that these areincluded within the scope of the invention.

Particular compounds according to the invention include those mentionedin the examples and their pharmaceutically acceptable derivatives.

As used herein “pharmaceutically acceptable derivative” includes anypharmaceutically acceptable salt, ester or salt of such ester of acompound of formula (I) which, upon administration to the recipient iscapable of providing (directly or indirectly) a compound of formula (I)or an active metabolic or residue thereof.

It will be appreciated that for use in medicine the salts of thecompounds of formula (I) should be pharmaceutically acceptable. Suitablepharmaceutically acceptable salts will be apparent to those skilled inthe art and include acid addition salts formed with inorganic acids e.g.hydrochloric, hydrobromic, sulphuric, nitric or phosphoric acid; andorganic acids e.g. succinic, maleic, acetic, fumaric, citric, tartaric,benzoic, p-toluenesulfonic, methanesulfonic or naphthalenesulfonic acid.Other salts e.g. oxalates, may be used, for example in the isolation ofcompounds of formula (I) and are included within the scope of thisinvention. Also included within the scope of the invention are solvatesand hydrates of compounds of formula (I).

Certain of the compounds of formula (I) may form acid addition saltswith one or more equivalents of the acid. The present invention includeswithin its scope all possible stoichiometric and non-stoichiometricforms.

Since the compounds of formula (I) are intended for use inpharmaceutical compositions it will readily be understood that they areeach preferably provided in substantially pure form, for example atleast 60% pure, more suitably at least 75% pure and preferably at least85%, especially at least 98% pure (% are on a weight for weight basis).Impure preparations of the compounds may be used for preparing the morepure forms used in the pharmaceutical compositions.

According to a further feature of the invention there is provided aprocess for the preparation of compounds of formula (I) and derivativesthereof. The following scheme details one of the synthetic routes tocompounds of the invention.

wherein Ar and R are as defined for compounds of formula (I), Yrepresents a (C₁₋₆)alkyl, R⁵ is an optionally substituted (C₁₋₆)alkylgroup, P¹ and P² are protecting groups and L¹ and L² are leaving groups.

Examples of protecting groups P¹ and P² include but are not restrictedto t-butyloxycarbonyl, trifluoroacetyl, benzyloxycarbonyl and optionallysubstituted benzyl. Deprotection conditions will depend on theparticular protecting group; for the groups mentioned above these arerespectively, acid (e.g. trifluoroacetic acid in dichloromethane), base(e.g. potassium carbonate in a solvent such as aqueous methanol) andcatalytic hydrogenolysis in an inert solvent (e.g. using palladium oncharcoal in a lower alcohol or ethyl acetate).

Examples of suitable leaving groups L¹ and L² include halogen, hydroxy,OC(═O)alkyl, OC(═O)O-alkyl and OSO₂Me. Acylation may be carried outusing a wide range of known conditions, e.g. in an inert solvent such asdichloromethane, in the presence of a base such as triethylamine.Alternatively these steps may be carried out when L¹ or L² representshydroxy, in which case the reaction takes place in an inert solvent suchas dichloromethane in the presence of a diimide reagent such as1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and anactivator such as 1-hydroxybenzotriazole.

Reduction of the amide can be carried out using known methods e.g. witha metal hydride reducing agent such as lithium aluminium hydride in aninert solvent such as diethyl ether or tetrahydrofuran.

Within scheme 1 the protecting groups P¹ and P² are chosen to bedifferent and there is scope for functional group interchange and use ofoptional protecting groups within Ar, R R¹, and for example when Y is H,preferably a protecting group is used.

wherein Ar is as defined for formula (I), Y represents a (C₁₋₆) alkyl, Rrepresents an optionally substituted heterocyclic ring system as definedfor formula (I), P¹ and P² are protecting groups and L¹ is a leavinggroup as described for Scheme 1. Formation of the urea bond may becarried out using methods known to those skilled in the art. Forexample, in an inert solvent such as dichloromethane ordimethylformamide, by reaction with a carbamoyl chloride reagent eitherdirectly, or generated in situ from suitable amines with reagents suchas phosgene or triphosgene. Alternatively this reaction may be carriedout with a suitable amine in an inert solvent in the presence ofdicarbonyl reagents such as 1,1′-carbonyldiimidazole.

The compounds of formula (I) may be prepared singly or as compoundlibraries comprising at least 2, e.g. 5 to 1000, preferably 10 to 100compounds of formula (I). Compound libraries may be prepared by acombinatorial ‘split and mix’ approach or by multiple parallel synthesisusing either solution phase or solid phase chemistry, by proceduresknown to those skilled in the art.

Thus according to a further aspect of the invention there is provided acompound library comprising at least 2 compounds of formula (I), orpharmaceutically acceptable derivatives thereof.

Pharmaceutically acceptable salts may be prepared conventionally byreaction with the appropriate acid or acid derivative.

The compounds of formula (I) and their pharmaceutically acceptablederivatives are useful for the treatment of diseases or disorders wherean antagonist of a human Orexin receptor is required such as obesity anddiabetes; prolactinoma; hypoprolactinemia; hypothalamic disorders ofgrowth hormone deficiency; idiopathic growth hormone deficiency;Cushing's syndrome/disease; hypothalamic-adrenal dysfunction; dwarfism;sleep disorders; sleep apnea; narcolepsy; insomnia; parasomnia; jet-lagsyndrome; sleep disturbances associated with diseases such asneurological disorders, neuropathic pain and restless leg syndrome;heart and lung diseases; depression; anxiety; addictions; obsessivecompulsive disorder; affective neurosis/disorder; depressiveneurosis/disorder; anxiety neurosis; dysthymic disorder; behaviourdisorder; mood disorder; sexual dysfunction; psychosexual dysfunction;sex disorder; sexual disorder; schizophrenia; manic depression;delerium; dementia; bulimia and hypopituitarism.

The compounds of formula (I) or pharmaceutically acceptable derivativesthereof are also useful in the treatment of stroke, particular ischaemicor haemorrhagic stroke. Furthermore the compounds of formula (I) orpharmaceutically acceptable derivatives useful in the blocking an emeticresponse.

The compounds of formula (I) and their pharmaceutically acceptablederivatives are particularly useful for the treatment of obesity,including obesity associated with Type 2 diabetes, and sleep disorders.Additionally the compounds are useful in stroke and/or blocking theemetic response i.e. nausea and vomiting. The compounds of formula (I)and pharmaceutically acceptable derivatives thereof are also useful inthe treatment of stroke, particularly ischaemic or haemorrhagic stroke.

Other diseases or disorders which may be treated in accordance with theinvention include disturbed biological and circadian rhythms;adrenohypophysis disease; hypophysis disease; hypophysis tumor/adenoma;adrenohypophysis hypofunction; functional or psychogenic amenorrhea;adrenohypophysis hyperfunction; migraine; hyperalgesia; pain; enhancedor exaggerated sensitivity to pain such as hyperalgesia, causalgia andallodynia; acute pain; burn pain; atypical facial pain; neuropathicpain; back pain; complex regional pain syndromes I and II; arthriticpain; sports injury pain; pain related to infection e.g. HIV, post-poliosyndrome and post-herpetic neuralgia; phantom limb pain; labour pain;cancer pain; post-chemotherapy pain; post-stroke pain; post-operativepain; neuralgia; and tolerance to narcotics or withdrawal fromnarcotics.

The invention also provides a method of treating or preventing diseasesor disorders where an antagonist of a human Orexin receptor is required,which comprises administering to a subject in need thereof an effectiveamount of a compound of formula (I), or a pharmaceutically acceptablederivative thereof.

The invention also provides a compound of formula (I), or apharmaceutically acceptable derivative thereof, for use in the treatmentor prophylaxis of diseases or disorders where an antagonist of a humanOrexin receptor is required.

The invention also provides the use of a compound of formula (I), or apharmaceutically acceptable derivatives thereof, in the manufacture of amedicament for the treatment or prophylaxis of diseases or disorderswhere an antagonist of a human Orexin receptor is required.

For use in therapy the compounds of the invention are usuallyadministered as a pharmaceutical composition. The invention alsoprovides a pharmaceutical composition comprising a compound of formula(I), or a pharmaceutically acceptable derivative thereof, and apharmaceutically acceptable carrier.

The compounds of formula (I) and their pharmaceutically acceptablederivatives may be administered by any convenient method, e.g. by oral,parenteral, buccal, sublingual, nasal, rectal or transdermaladministration, and the pharmaceutical compositions adapted accordingly

The compounds of formula (I) and their pharmaceutically acceptablederivatives which are active when given orally can be formulated asliquids or solids, e.g. as syrups, suspensions, emulsions, tablets,capsules or lozenges.

A liquid formulation will generally consist of a suspension or solutionof the active ingredient in a suitable liquid carrier(s) e.g. an aqueoussolvent such as water, ethanol or glycerine, or a non-aqueous solvent,such as polyethylene glycol or an oil. The formulation may also containa suspending agent, preservative, flavouring and/or colouring agent.

A composition in the form of a tablet can be prepared using any suitablepharmaceutical carrier(s) routinely used for preparing solidformulations, such as magnesium stearate, starch, lactose, sucrose andcellulose.

A composition in the form of a capsule can be prepared using routineencapsulation procedures, e.g. pellets containing the active ingredientcan be prepared using standard carriers and then filled into a hardgelatin capsule; alternatively a dispersion or suspension can beprepared using any suitable pharmaceutical carrier(s), e.g. aqueousgums, celluloses, silicates or oils and the dispersion or suspensionthen filled into a soft gelatin capsule.

Typical parenteral compositions consist of a solution or suspension ofthe active ingredient in a sterile aqueous carrier or parenterallyacceptable oil, e.g. polyethylene glycol, polyvinyl pyrrolidone,lecithin, arachis oil or sesame oil. Alternatively, the solution can belyophilised and then reconstituted with a suitable solvent just prior toadministration.

Compositions for nasal administration may conveniently be formulated asaerosols, drops, gels and powders. Aerosol formulations typicallycomprise a solution or fine suspension of the active ingredient in apharmaceutically acceptable aqueous or non-aqueous solvent and areusually presented in single or multidose quantities in sterile form in asealed container which can take the form of a cartridge or refill foruse with an atomising device. Alternatively the sealed container may bea disposable dispensing device such as a single dose nasal inhaler or anaerosol dispenser fitted with a metering valve. Where the dosage formcomprises an aerosol dispenser, it will contain a propellant which canbe a compressed gas e.g. air, or an organic propellant such as afluorochlorohydrocarbon or hydrofluorocarbon. Aerosol dosage forms canalso take the form of pump-atomisers.

Compositions suitable for buccal or sublingual administration includetablets, lozenges and pastilles where the active ingredient isformulated with a carrier such as sugar and acacia, tragacanth, orgelatin and glycerin.

Compositions for rectal administration are conveniently in the form ofsuppositories containing a conventional suppository base such as cocoabutter.

Compositions suitable for transdermal administration include ointments,gels and patches.

Preferably the composition is in unit dose form such as a tablet,capsule or ampoule.

The dose of the compound of formula (I), or a pharmaceuticallyacceptable derivative thereof, used in the treatment or prophylaxis ofthe abovementioned disorders or diseases will vary in the usual way withthe particular disorder or disease being treated, the weight of thesubject and other similar factors. However, as a general rule, suitableunit doses may be 0.05 to 1000 mg, more suitably 0.05 to 500 mg. Unitdoses may be administered more than once a day for example two or threetimes a day, so that the total daily dosage is in the range of about0.01 to 100 mg/kg; and such therapy may extend for a number of weeks ormonths. In the case of pharmaceutically acceptable derivatives the abovefigures are calculated as the parent compound of formula (I).

No toxicological effects are indicated/expected when a compound offormula (I) is administered in the above mentioned dosage range.

Human Orexin-A has the amino acid sequence: pyroGlu Pro Leu Pro Asp CysCys Arg Gln Lys Thr  1              5                 10 Cys Ser Cys ArgLeu Tyr Glu Leu Leu His Gly Ala       15                        20 GlyAsn His Ala Ala Gly Ile Leu Thr Leu-NH₂    25                 30

Orexin-A can be employed in screening procedures for compounds whichinhibit the ligand's activation of the orexin-1 receptor.

In general, such screening procedures involve providing appropriatecells which express the orexin-1 receptor on their surface. Such cellsinclude cells from mammals, yeast, Drosophila or E. coli. In particular,a polynucleotide encoding the orexin-1 receptor is used to transfectcells to express the receptor. The expressed receptor is then contactedwith a test compound and an orexin-1 receptor ligand to observeinhibition of a functional response. One such screening procedureinvolves the use of melanophores which are transfected to express theorexin-1 receptor, as described in WO 92/01810.

Another screening procedure involves introducing RNA encoding theorexin-1 receptor into Xenopus oocytes to transiently express thereceptor. The receptor oocytes are then contacted with a receptor ligandand a test compound, followed by detection of inhibition of a signal inthe case of screening for compounds which are thought to inhibitactivation of the receptor by the ligand.

Another method involves screening for compounds which inhibit activationof the receptor by determining inhibition of binding of a labelledorexin-1 receptor ligand to cells which have the receptor on theirsurface. This method involves transfecting a eukaryotic cell with DNAencoding the orexin-1 receptor such that the cell expresses the receptoron its surface and contacting the cell or cell membrane preparation witha compound in the presence of a labelled form of an orexin-1 receptorligand. The ligand may contain a radioactive label. The amount oflabelled ligand bound to the receptors is measured, e.g. by measuringradioactivity.

Yet another screening technique involves the use of FLIPR equipment forhigh throughput screening of test compounds that inhibit mobilisation ofintracellular calcium ions, or other ions, by affecting the interactionof an orexin-1 receptor ligand with the orexin-1 receptor.

All publications, including but not limited to patents and patentapplications, cited in this specification are herein incorporated byreference as if each individual publication were specifically andindividually indicated to be incorporated by reference herein as thoughfully set forth.

The following Examples illustrate the preparation of pharmacologicallyactive compounds of the invention. The Descriptions D1-D11b illustratethe preparation of intermediates to compounds of the invention.

Description 1:(RS)-1-Benzyl-4-(tert-butyloxycarbonyl)-2-carbamoylpiperazine

A solution of (RS)-1-(tert-butyloxycarbonyl)-3-carbamoylpiperazine (refBruce et al. Syn. Comm. 1995, 2673-84) (25 g, 0.109 mol) andbenzaldehyde (11.1 ml, 0.109 mol) in 1,2-dichloroethane (550 ml) wasstirred at room temperature for 1.5 h. Sodium triacetoxyborohydride(34.7 g, 0.163 mol) was added in one portion and the resultant stirredfor a further 18 h. Dichloromethane (400 ml) was added and the mixturewashed with saturated sodium hydrogen carbonate (600 ml). The organiclayer was dried (Na₂SO₄) and evaporated in vacuo. The residue waschromatographed on silica gel eluting with 10-70% ethyl acetate inhexane to afford the title compound as a colourless solid (32.4 g, 93%).

¹H NMR (CDCl₃) δ: 1.45 (9H, s), 2.15 (1H, dt), 2.75-3.15 (4H, m), 3.28(1H, d, J=14 Hz), 3.85 (1H, broad d), 3.96 (1H, d, J=14 Hz), 4.15 (1H,broad m), 5.63 (1H, broad s), 6.70 (1H, broad s), 7.2-7.5 (5H, m).

Description 2: (RS)-2-Aminomethyl-1-benzyl-4-methylpiperazine

1M Lithium aluminium hydride in tetrahydrofuran (112 ml, 0.112 mol) wasadded dropwise to a stirred solution of(RS)-1-benzyl-4-(tert-butyloxycarbonyl)-2-carbamoylpiperazine (D1) (15g, 0.047 mol) in anhydrous tetrahydrofuran (300 ml) at room temperatureunder argon. On complete addition the reaction mixture was stirred atroom temperature for 0.5 h, then at reflux for a further 1.5 h. Themixture was cooled to room temperature and treated sequentially withwater (19.5 ml), 2N sodium hydroxide (22.5 ml) and water (19.5 ml)dropwise. Sodium sulphate was added and the resultant stirred for 0.3 h,filtered and the filtrate evaporated in vacuo to give the title compound(10.3 g, 100%).

Mass spectrum (AP⁺): Found 220 (ME). C₁₃H₂₁N₃ requires 219.

Description 3:(RS)-1-Benzyl-4-methyl-2-(trifluoroacetylaminomethyl)piperazine

Trifluoroacetic anhydride (8.05 ml, 0.057 mol) in anhydrousdichloromethane (10 ml) was added dropwise to a stirred solution of(RS)-2-aminomethyl-1-benzyl-4-methylpiperazine (D2) (10.3 g, 0.047 mol)and triethylamine (9.25 ml, 0.066 mol) in anhydrous dichloromethane (400ml) at 0° C. under argon. The resultant was stirred at 0° C. for 1 h,then at room temperature for 18 h. The mixture was washed with saturatedsodium hydrogen carbonate (400 ml) and the organic layer dried (Na₂SO₄)and evaporated in vacuo. The residue was chromatographed on silica geleluting with 50% ethyl acetate in hexane, then 0-10% methanol in ethylacetate to yield the title compound as a pale green gum (6.06 g, 41%).

Mass spectrum (AP⁺): Found 316 (MH⁺). C₁₅H₂₀F₃N₃O requires 315.

Description 4: (RS)-4-Methyl-2-(trifluoroacetylaminomethyl)piperazine

A solution of(RS)-1-benzyl-4-methyl-2-(trifluoroacetylaminomethyl)piperazine (D3)(6.06 g, 0.0192 mol) in ethanol (300 ml) was hydrogenated at atmosphericpressure in the presence of 10% palladium on charcoal (6 g, 54% pastewith water) for 18 h. The mixture was filtered through Kieselguhr andthe filtrate evaporated in vacuo to furnish the title compound as acolourless gum (4.07 g, 94%).

Mass spectrum (AP⁺): Found 226 (MH⁺). C₈₁H₄F₃N₃O requires 225.

Description 5:(RS)-1-((4-(5-(4-Fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4-methyl-2-(trifluoroacetylaminomethyl)piperazine

A solution of 5-(4-fluorophenyl)-2-methylthiazole-4-carbonyl chloride(2.27 g, 8.9 mmol) in dichloromethane (20 ml) was added dropwise withice cooling to a stirred solution of(RS)-4-methyl-2-(trifluoroacetylaminomethyl)piperazine (D4) (2 g, 8.9mmol) and triethylamine (3.71 ml, 26.6 mmol) in dichloromethane (80 ml).On complete addition, cooling was removed and the reaction mixturestirred at room temperature for 2.5 h, washed with saturated sodiumhydrogen carbonate and the organic layer dried (Na₂SO₄) and evaporatedin vacuo. The residue was chromatographed on silica gel eluting with0-5% methanol in dichloromethane to afford the title compound as acolourless solid (3.5 g, 89%).

Mass spectrum (AP⁺): Found 445 (MH⁺). C₁₉H₂₀F₄N₄O₂S requires 444.

Description 6:(RS)-2-Aminomethyl-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4-methylpiperazine

A mixture of(RS)-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4-methyl-2-(trifluoroacetylaminomethyl)piperazine(D5) (3.65 g, 8.2 mmol) and potassium carbonate (6 g, 43.5 mmol) inmethanol (300 ml) and water (100 ml) was heated at reflux for 1.5 h. Thereaction mixture was cooled to room temperature, evaporated in vacuo andthe residue partitioned between brine (500 ml) and dichloromethane (150ml). The aqueous layer was extracted with dichloromethane (3×150 ml) andthe combined organic extracts dried (Na₂SO₄) and evaporated in vacuo toafford the title compound as a pale green gum (2.18 g, 76%).

Mass spectrum (AP⁺): Found 349 (MH⁺). C₁₇H₂₁FN₄OS requires 348.

Description 7 (a):(RS)-2-((Benzofuran-7-yl)carbonylaminomethyl)-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)₄-methylpiperazine

A mixture of(RS)-2-aminomethyl-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4-methylpiperazine(D6) (0.29 g, 0.83 mmol), benzofuran-7-carboxylic acid (0.148 g, 0.91mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride(0.176 g, 0.91 mmol) and 1-hydroxybenzotriazole hydrate (0.02 g, 0.13mmol) in dichloromethane (8 ml) was shaken for 18 hrs. The reactionmixture was washed with saturated sodium hydrogen carbonate (6 ml) andthe organic layer added directly onto a 10 g pre-packed silica gelcartridge. Elution with 0-100% ethyl acetate in hexane, then 1-10%methanol in ethyl acetate afforded the title compound as a colourlessamorphous solid (0.29 g, 71%).

Mass spectrum (Electrospray LC/MS): Found 493 (MH⁺). C₂₆H₂₅FN₄O₃Srequires 492.

The following compounds were prepared in a similar manner to Description7 (a)

7(b):(RS)-2-((5-Fluorobenzofuran-7-yl)carbonylaminomethyl)-S-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4-methylpiperazine

Mass spectrum (Electrospray LC/MS): Found 511 (MH⁺). C₂₆H₂₄F₂N₄O₃Srequires 510.

7(c):(RS)-1-((4-(5-(4-Fluorophenyl)-2-methyl)thiazolyl)carbonyl)-2-((6-methoxybenzofuran-4-yl)carbonylaminomethyl)-4-methylpiperazine

Mass spectrum (Electrospray LC/MS): Found 523 (MX>). C₂₇H₂₇FN₄O₄Srequires 522.

7(d):(RS)-1-((4-(5-(4-Fluorophenyl)-2-methyl)thiazolyl)carbonyl)-2-((7-methoxybenzofuran-4-yl)carbonylaminomethyl)-4-methylpiperazine

Mass spectrum (Electrospray LC/MS): Found 523 (MH⁺). C₂₇H₂₇FN₄O₄Srequires 522.

2-Aminomethyl-1-(benzyloxycarbonyl)-4-(tert-butyloxycarbonyl)piperazinewas synthesised from piperazine-2-carboxylic acid as described inPCT/US0017472 (WO 01/00214) except that1-(benzyloxycarbonyl)-2-hydroxymethyl-4-(tert-butyloxycarbonyl)-piperazinewas prepared as described below.

Description 8:(R)-1-(Benzyloxycarbonyl)-2-hydroxymethyl-4-(tert-butyloxycarbonyl)-piperazine

To(S)-1-(benzyloxycarbonyl)₄-(tert-butyloxycarbonyl)-piperazine-2-carboxylicacid (15.2 g, 0.04 mol) in tetrahydrofuran (200 ml) at 0° C. under argonwas added borane (1M soln. in THF; 111 ml, 0.11 mol) dropwise over 15min. The resulting mixture was stirred for 1 h, maintaining thetemperature between 0° C. and 5° C., and then allowed to reach roomtemperature and stirred a further 18 h. The mixture was then carefullyadded, with stirring, to 5% g. acetic acid in water (1 l). After 1 h,the organics were evaporated in vacuo and the residual aqueous extractedwith ethyl acetate (300 ml×4). The combined extracts were dried(Na₂SO₄), and evaporated in vacuo to a colourless oil. Chromatography onsilica gel eluting with ethyl acetate-hexane mixtures afforded the titleproduct (11 g, 75%) as a colourless oil.

Mass spectrum (AP⁺): Found 351 (MH⁺). C₁₈H₂₆N₂O₅ requires 350.

Description 9:(R)-1-(Benzyloxycarbonyl)-4-(tert-butyloxycarbonyl)-2-(((1-(6-fluoro-2,3-dihydro-indol-1-yl)carbonyl)amino)methyl)-piperazine

(R)-2-Aminomethyl-1-(benzyloxycarbonyl)-4-(tert-butyloxycarbonyl)piperazine(0.4 g, 1.15 mmol) in dichloromethane (10 ml) was added dropwise underargon to a stirred solution of 1,1′-carbonyldiimidazole (0.186 g, 1.15mmol) in dichloromethane (10 ml) at room temperature. After 1.5 h, theresulting mixture was evaporated in vacuo and to the residue indimethylformamide (10 ml) was added 5-fluoroindoline (0.157 g, 1.15mmol) and the reaction mixture heated at 100° C. for 5 h. After coolingto room temperature and stirring for 18 h, the reaction mixture waspoured into water and extracted twice with ether. The combined extractswere dried and evaporated in vacuo and the residue chromatographed onsilica gel, eluting with a 10% ethyl acetate/hexane to 2% methanol/ethylacetate gradient to afford the title product (0.5 g, 85%). Mass spectrum(AP⁺): Found 513 (MH⁺). C₂₇H₃₃FN₄O₅ requires 512.

Description 10:(R)-1-(tert-Butyloxycarbonyl)-3-(((1-(6-fluoro-2,3-dihydro-indol-1-yl)carbonyl)amino)methyl)-piperazine

The product of D9 (0.5 g, 0.98 mmol) in ethanol (15 ml) was hydrogenatedat NTP over 10% Pd/C (0.2 g, 50% aq. paste) for 7.75 h, filtered throughkieselguhr, washing with ethanol and the filtrate evaporated to affordthe title compound (0.39 g, 100%) which was used without furtherpurification. Mass spectrum (AP⁺): Found 379 (MH⁺). C₁₉H₂₇FN₄O₃ requires378.

Description 11(a):(R)-1-(tert-Butyloxycarbonyl)-3-(((1-(6-fluoro-2,3-dihydro-indol-1-yl)carbonyl)amino)methyl)-4-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)piperazine

5-(4-Fluorophenyl)-2-methylthiazole-4-carbonyl chloride (0.044 g, 0.19mmol) in dichloromethane (1 ml) was added to a solution of D10 (0.06 g,0.16 mmol) and triethylamine (0.11 ml, 0.8 mmol) in dichloromethane (2ml) and the mixture stirred for 18 h at room temperature. The reactionmixture was washed with saturated sodium hydrogen carbonate and theorganic layer applied directly to a 10 g pre-packed silica gel cartridgeand eluted with an ethyl acetate-hexane gradient to afford the titlecompound (0.075 g, 75%). Mass spectrum (AP⁺): Found 598 (MH⁺).C₃₀H₃₃F₂N₅O₄S requires 597.

The following compound was prepared in a similar manner to Description11(a).

11(b):(R)-1-(tert-Butyloxycarbonyl)-3-(((1-(6-fluoro-2,3-dihydro-indol-1-yl)carbonyl)amino)methyl)-4-((2-(2-furanyl)phenyl)carbonyl)-piperazine

Mass spectrum (AP⁺): Found 549 (MH⁺). C₃₀H₃₃FN₄O₅ requires 548.

EXAMPLE 1(RS)-2-((Benzofuran-4-yl)carbonylaminomethyl)-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4-methylpiperazine

A mixture of(RS)-2-aminomethyl-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4-methylpiperazine(D6) (0.348 g, 1 mmol), benzofuran-4-carboxylic acid (0.162 g, 1 mmol),1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (0.192 g, 1mmol) and 1-hydroxybenzotriazole hydrate (0.02 g, 0.13 mmol) indichloromethane (30 ml) was stirred for 18 h at room temperature. Thereaction mixture was washed with saturated sodium hydrogen carbonate (30ml) and the organic layer dried (Na₂SO₄) and evaporated in vacuo. Theresidue was chromatographed on silica gel eluting with 0-100% ethylacetate in hexane, then 1-10% methanol in ethyl acetate to afford thetitle compound as a colourless amorphous solid (0.344 g, 70%). Massspectrum (Electrospray LC/MS): Found 493 (MH⁺). C₂₆H₂₅FN₄O₃S requires492.

The compounds of the Examples below were prepared from the appropriateamine and acid using a similar process to that described in Example 1.

Example Ar R Mass Spectrum (Electrospray LC/MS) 2

Found MH⁺: 504. C₂₇H₂₆FN₅O₂S requires 503. 3

Found MH⁺: 523. C₂₇H₂₇FN₄O₄S requires 522.

EXAMPLE 4(RS)-2-((Benzofuran-4-yl)carbonylaminomethyl)-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)piperazine

To a stirred solution of(RS)-2-((benzofuran-4-yl)carbonylaminomethyl)-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-4-methylpiperazine(product of Example 1) (0.35 g, 0.67 mmol) in 1,2-dichloromethane (6 ml)at 0° C. under argon was added 1-chloroethyl chloroformate (0.45 ml, 4.1mmol) dropwise. The resultant mixture was stirred at 0° C. for 0.1 h,allowed to warm to room temperature over 0.5 h then heated at 65° C. for20 h. The mixture was cooled to room temperature, diisopropylethylamine(2 ml) added and heated at gentle reflux for 1.5 h. On cooling, themixture was evaporated in vacuo and the residue dissolved in methanol(10 ml) and heated at reflux for 2 h. The mixture was recooled,evaporated in vacuo and the residue partitioned between dichloromethaneand saturated sodium hydrogen carbonate (100 ml of each). The aqueouslayer was extracted with dichloromethane (100 ml) and the combinedorganics dried (Na₂SO₄) and evaporated in vacuo. The residue waschromatographed on silica gel eluting with 0-100% ethyl acetate inhexane, then 1-30% methanol in ethyl acetate to afford the titlecompound as a pale brown amorphous solid (0.135 g, 40%). Mass spectrum(Electrospray LC/MS): Found 479 (MH⁺). C₂₅H₂₃FN₄O₃S requires 478.

The racemic product of Example 4 was separated into its individualenantiomers using the following procedure. Racemate (135 mg) wasdissolved in 20% v/v ethanol in n-hexane to a concentration of 5.0mgml⁻¹. A 2 ml aliquot of this solution was applied to a Chiracel OD(250 mm×20 mm i.d.) chromatography column. Elution with 20% V/v ethanolin n-hexane at a flow rate of 17 mlmin⁻¹ using U.V. detection at 215 nmafforded the individual enantiomers. Repeat injection of 2 ml aliquots,pooling of relevant fractions and evaporation of the pooled fractions invacuo afforded the following:

EXAMPLE (4A) Faster Running Enantiomer (41 mg). Mass spectrum (AP⁺):Found 479 (MH⁺). C₂₅H₂₃FN₄O₃S requires 478. Enantiomeric purity 98.8%e.e. EXAMPLE (4B) Slower Running Enantiomer (46 mg). Mass spectrum(AP⁺): Found 479 (MH⁺). C₂₅H₂₃FN₄O₃S requires 478. Enantiomeric purity94.0% e.e.

The compounds of the Examples below were prepared from the appropriatepiperazine using a similar process to that described in Example 4.

Example Ar R Mass Spectrum (Electrospray LC/MS) 5

Found MH⁺: 479. C₂₅H₂₃FN₄O₃S requires 478. 6

Found MH⁺: 497. C₂₅H₂₂F₂N₄O₃S requires 496. 7

Found MH⁺: 490. C₂₆H₂₄FN₅O₂S requires 489. 8

Found MH⁺: 509. C₂₆H₂₅FN₄O₄S requires 508. 9

Found MH⁺: 509. C₂₆H₂₅FN₄O₄S requires 508. 10

Found MH⁺: 509. C₂₆H₂₅FN₄O₄S requires 508.

EXAMPLE 11(S)-2-(((1-(6-Fluoro-2,3-dihydro-indol-1-yl)carbonyl)amino)methyl)-1-((4-(5-(4-fluorophenyl)-2-methyl)thiazolyl)carbonyl)-piperazinetrifluoroacetate

To a solution of D₁₁(a) (0.075 g, 0.13 mmol) in dichloromethane (10 ml)was added trifluoroacetic acid (2 ml) at room temperature. After 3 h,the reaction mixture was evaporated to afford the title product (0.08 g,99%).

Mass spectrum (Electrospray LC/MS): Found 498 (MH⁺). C₂₅H₂₅F₂N₅O₂Srequire 497.

EXAMPLE 12(S)-2-(((1-(6-Fluoro-2,3-dihydro-indol-1-yl)carbonyl)amino)methyl)-1-((2-(2-furanyl)phenyl)carbonyl)-piperazinetrifluoroacetate

The title compound (0.029 g, 88%) was prepared from D11 (b) using themethod of Example 11.

Mass spectrum (Electrospray LC/MS): Found 449 (MH⁺). C₂₅H₂₅FN₄O₃requires 448.

It is understood that the present invention covers all combinations ofparticular and preferred groups described herein above.

Determination of Orexin-1 Receptor Antagonist Activity

The orexin-1 receptor antagonist activity of the compounds of formula(I) was determined in accordance with the following experimental method.

Experimental Method

CHO-DG44 cells expressing the human orexin-1 receptor were grown in cellmedium (MEM medium with Earl's salts) containing 2 mM L-Glutamine, 0.4mg/mL G418 Sulphate from GIBCO BRL and 10% heat inactivated fetal calfserum from Gibco BRL. The cells were seeded at 20,000 cells/100 Pd/wellinto 96-well black clear bottom sterile plates from Costar which hadbeen pre-coated with 10 μg/well of poly-L-lysine from SIGMA. The seededplates were incubated overnight at 37° C. in 5% CO₂.

Agonists were prepared as 1 mM stocks in water:DMSO (1:1). EC₅₀ values(the concentration required to produce 50% maximal response) wereestimated using 1× half log unit dilutions (Biomek 2000, Beckman) inTyrode's buffer containing probenecid (10 mM HEPES with 145 mM NaCl, 10mM glucose, 2.5 mM KCl, 1.5 mM CaCl₂, 1.2 mM MgCl₂ and 2.5 mMprobenecid; pH7.4). Antagonists were prepared as 10 mM stocks in DMSO(100%). Antagonist IC₅₀ values (the concentration of compound needed toinhibit 50% of the agonist response) were determined against 3.0 nMhuman orexin-A using 11× half log unit dilutions in Tyrode's buffercontaining 10% DMSO and probenecid.

On the day of assay 50 μl of cell medium containing probenecid (Sigma)and Fluo3AM (Texas Fluorescence Laboratories) was added (Quadra, Tomtec)to each well to give final concentrations of 2.5 mM and 4 μM,respectively. The 96-well plates were incubated for 60 min at 37° C. in5% CO₂. The loading solution containing dye was then aspirated and cellswere washed with 4×150 μl Tyrode's buffer containing probenecid and 0.1%gelatin (Denley Cell Wash). The volume of buffer left in each well was125 μl. Antagonist or buffer (25 μl) was added (Quadra) the cell platesgently shaken and incubated at 37° C. in 5% CO₂ for 30 minutes. Cellplates were then transferred to the Fluorescent Imaging Plate Reader(FLIPR, Molecular Devices) instrument. Prior to drug addition a singleimage of the cell plate was taken (signal test), to evaluate dye loadingconsistency. The run protocol used 60 images taken at 1 second intervalsfollowed by a further 24 images at 5 second intervals. Agonists wereadded (by the FLIPR) after 20 seconds (during continuous reading). Fromeach well, peak fluorescence was determined over the whole assay periodand the mean of readings 1-19 inclusive was subtracted from this figure.The peak increase in fluorescence was plotted against compoundconcentration and iteratively curve fitted using a four parameterlogistic fit (as described by Bowen and Jerman, TiPS, 1995, 16, 413-417)to generate a concentration effect value. Antagonist Kb values werecalculated using the equation:Kb=IC ₅₀/(1+([3/EC ₅₀])

where EC₅₀ was the potency of human orexin-A determined in the assay (innM terms) and IC₅₀ is expressed in molar terms.

Compounds of Examples tested according to this method had pKb values inthe range 7.0 to 8.7 at the human cloned orexin-1 receptor.

The orexin-2 receptor antagonist activity of the compounds of formula(I) was determined in accordance with the following experimental method.

Experimental Method

CHO-DG44 cells expressing the human orexin-2 receptor were grown in cellmedium (MEM medium with Earl's salts) containing 2 mM L-Glutamine, 0.4mg/mL G418 Sulphate from GIBCO BRL and 10% heat inactivated fetal calfserum from Gibco BRL. The cells were seeded at 20,000 cells/100 μl/wellinto 96-well black clear bottom sterile plates from Costar which hadbeen pre-coated with 10 μg/well of poly-L-lysine from SIGMA. The seededplates were incubated overnight at 37° C. in 5% CO₂.

Agonists were prepared as 1 mM stocks in water:DMSO (1:1). EC₅₀ values(the concentration required to produce 50% maximal response) wereestimated using 1× half log unit dilutions (Biomek 2000, Beckman) inTyrode's buffer containing probenecid (10 mM HEPES with 145 mM NaCl, 10mM glucose, 2.5 mM KCl, 1.5 mM CaCl₂, 1.2 mM MgCl₂ and 2.5 mMprobenecid; pH7.4). Antagonists were prepared as 10 mM stocks in DMSO(100%). Antagonist IC₅₀ values (the concentration of compound needed toinhibit 50% of the agonist response) were determined against 10.0 nMhuman orexin-A using 11× half log unit dilutions in Tyrode's buffercontaining 10% DMSO and probenecid.

On the day of assay 50 μl of cell medium containing probenecid (Sigma)and Fluo3AM (Texas Fluorescence Laboratories) was added (Quadra, Tomtec)to each well to give final concentrations of 2.5 mM and 4 μM,respectively. The 96-well plates were incubated for 60 min at 37C in 5%CO₂. The loading solution containing dye was then aspirated and cellswere washed with 4×150 μl Tyrode's buffer containing probenecid and 0.1%gelatin (Denley Cell Wash). The volume of buffer left in each well was125 μl. Antagonist or buffer (25 μl) was added (Quadra) the cell platesgently shaken and incubated at 37C in 5% CO₂ for 30 min. Cell plateswere then transferred to the Fluorescent Imaging Plate Reader (FLIPR,Molecular Devices) instrument. Prior to drug addition a single image ofthe cell plate was taken (signal test), to evaluate dye loadingconsistency. The run protocol used 60 images taken at 1 second intervalsfollowed by a further 24 images at 5 second intervals. Agonists wereadded (by the FLIPR) after 20 sec (during continuous reading). From eachwell, peak fluorescence was determined over the whole assay period andthe mean of readings 1-19 inclusive was subtracted from this figure. Thepeak increase in fluorescence was plotted against compound concentrationand iteratively curve fitted using a four parameter logistic fit (asdescribed by Bowen and Jerman, TiPS, 1995, 16, 413-417) to generate aconcentration effect value. Antagonist Kb values were calculated usingthe equation:Kb=IC ₅₀/(1+([3/EC ₅₀])

where EC₅₀ was the potency of human orexin-A determined in the assay (innM terms) and IC₅₀ is expressed in molar terms.

Compounds of Examples tested according to this method had pKb values inthe range <6.5 to 7.0 at the human cloned orexin-2 receptor.

Throughout the specification and the claims which follow, unless thecontext requires otherwise, the word ‘comprise’, and variations such as‘comprises’ and ‘comprising’, will be understood to imply the inclusionof a stated integer or step or group of integers but not to theexclusion of any other integer or step or group of integers or steps.

The application of which this description and claims forms part may beused as a basis for priority in respect of any subsequent application.The claims of such subsequent application may be directed to any featureor combination of features described herein. They may take the form ofproduct, composition, process, or use claims and may include, by way ofexample and without limitation the following claims:

1. A compound of formula (I):

wherein: Y represents hydrogen or (C₁₋₆) alkyl; Ar represents an arylgroup or a 5- or 6-membered heterocyclic ring containing up to 3heteroatoms selected from N, O and S, wherein the aryl or heterocyclicgroup is substituted by R¹ and further optional substituents; R¹represents optionally substituted (C₁₋₆)alkoxy, halo, optionallysubstituted (C₁₋₆)alkyl, cyano, optionally substituted phenyl or anoptionally substituted 5- or 6-membered heterocyclic ring containing upto 4 heteroatoms selected from N, O and S; R represents an optionallysubstituted aryl or an optionally substituted heterocyclic ring systemcontaining up to 4 heteroatoms selected from N, O and S; or apharmaceutically acceptable salt thereof.
 2. A compound according toclaims 1 wherein Y is hydrogen or methyl.
 3. A compound as claimed inclaim 1 wherein Ar represents optionally substituted thiazolyl.
 4. Acompound according to claim 1 wherein Ar is optionally substituted by ahalogen or optionally substituted phenyl, optionally substituted(C₁₋₆)alkyl or optionally substituted (C₁₋₆)alkoxy.
 5. A compoundaccording to claim 1 wherein Ar is optionally substituted by methyl. 6.A compound according to claim 1 wherein R¹ represents an optionallysubstituted phenyl.
 7. A compound according to claim 1 wherein R¹ isoptionally substituted by a halogen, optionally substituted (C₁₋₆)alkylor optionally substituted (C₁₋₆)alkoxy.
 8. A compound according to claim1 wherein R¹ is optionally substituted by fluorine.
 9. A compoundaccording to claim 1 wherein R represents an optionally substitutedbenzofuranyl, quinolinyl or indolinyl.
 10. A compound according to claim1 wherein R is optionally substituted by a halogen, or optionallysubstituted (C₁₋₆)alkoxy.
 11. A compound according to claim 10 whereinoptional substituents of R are methoxy and fluorine.
 12. A compound offormula (I) as defined in any one of Examples 1 to 12, or apharmaceutically acceptable salt of any one thereof.
 13. Apharmaceutical composition comprising a compound of formula (I) asdefined in claim 1, or a pharmaceutically acceptable salt thereof, and apharmaceutically acceptable carrier.
 14. A method of treating orpreventing disease or disorders where an antagonist of a human orexinreceptor is required, which comprises administering to a subject in needthereof an effective amount of a compound of formula (I) as defined inclaim 1, or a pharmaceutically acceptable salt thereof.